President Trump on Tuesday belittled former foreign policy adviser George Papadopoulos, who pleaded guilty this week to lying to federal agents investigating Russia's interference in the 2016 election, tweeting that "few people knew the young, low level volunteer named George, who has already proven to be a liar."

But interviews and documents show that Papadopoulos was in regular contact with the Trump campaign's most senior officials and held himself out as a Trump surrogate as he traveled the world to meet with foreign officials and reporters.

Papadopoulos sat at the elbow of one of Trump's top campaign advisers, then-Sen. Jeff Sessions, during a dinner for campaign advisers weeks before the Republican National Convention, according to an individual who attended the meeting.

He met in London in September 2016 with a mid-level representative of the British Foreign Office, where he said he had contacts at the senior level of the Russian government.

And he conferred at one point with the foreign minister of Greece at a meeting in New York.

Emails included in court documents released Monday show that Papadopoulos repeatedly told Trump campaign officials about his contacts with people he believed were representing the Russian government.

The court documents do not answer a key question: whether Papadopoulos also told his superiors that he had met a London-based professor who claimed to know that the Russians had "dirt" on Democratic candidate Hillary Clinton, including thousands of her emails.

An FBI agent told the court in July that Papadopoulos lied in an interview with federal agents, saying he did not tell anyone on the campaign about the "dirt" because he thought the professor was a "nothing."

At 29, Papadopoulos had scant experience that qualified him to advise a presidential candidate. He had entered the Trump campaign after a six-week stint working for the campaign of Trump's rival for the Republican nomination, neurosurgeon Ben Carson.

At the time, Carson's campaign was desperate to show it had policy experts advising his campaign, given that most leading Republican foreign policy thinkers had been snapped up by other candidates.

Bennett said his only vetting was to ask a friend at the Washington-based Hudson Institute, where Papadopoulos's résumé indicated he had worked as a researcher, whether Papadopoulos was "an okay guy."

"I wasn't looking for something stellar," Bennett said. "I wanted to make sure he was okay."

For six weeks of work, Bennett said, Papadopoulos was paid $8,500, before he was let go from the campaign at the end of January 2016 as it shed staff.

By March 2016, Trump's campaign, like Carson's before it, was eagerly searching for foreign policy expertise. As Trump rose in the polls and won Republican primaries, the former reality TV host was under pressure to announce a group of advisers with whom he was consulting on foreign policy issues.

The scrutiny intensified early that month after 70 conservative national security experts signed an open letter opposing Trump's candidacy. In mid-March, Trump was asked on the MSNBC show "Morning Joe" to name people with whom he spoke about foreign affairs.

"I'm speaking with myself, number one, because I have a very good brain," Trump responded, prompting more calls for a list of formal advisers.

To come up with names, the campaign turned to Sam Clovis, a former Iowa radio host who served as national campaign co-chairman, an attorney for Clovis confirmed Tuesday in a statement.

But the statement did not address how Papadopoulos ended up on the list. Bennett said he was not consulted and would not have recommended his former employee if he had been asked because he found him unimpressive.

On March 21, Trump included Papadopoulos among five men he announced were advising him on matters of national security in a meeting with The Washington Post editorial board. "An energy and oil consultant. Excellent guy," Trump said.

If Trump or his team had undertaken even a cursory vetting of Papadopoulos, they would have found that much of his already-slim résumé was either exaggerated or false.

While he claimed to have served for several years as a fellow at the Hudson Institute, officials there said he had been an unpaid intern and a researcher under contract to several fellows who were writing a book.

Although he claimed to be "U.S. Representative at the 2012 Geneva International Model United Nations," officials at that organization said they had no record of him.

Papadopoulos said he had delivered the "keynote address" at a leading American-Greek organization in 2008 — while a student at DePaul University. But records from the gathering indicate he merely participated in a youth panel with other participants. The keynote was delivered by 1988 Democratic presidential candidate Michael Dukakis.

Though Papadopoulos's exaggerated résumé issues quickly became public, he remained a part of the Trump advisory panel and soon began urging campaign aides to let him set up a meeting between Trump and Russian officials.

Court documents show he raised the idea at a March 31 meeting of the group attended by both Trump and Sessions, who had endorsed Trump's campaign, telling the group that "he had connections that could help arrange a meeting between then-candidate Trump and President [Vladimir] Putin."

He also began appearing in the foreign press. While visiting Israel the next month, he told a group of researchers that Trump saw Putin as "a responsible actor and potential partner," according to a column in the Jerusalem Post.

In May, he told the Telegraph of London that Prime Minister David Cameron should apologize to Trump for calling the candidate "divisive, stupid and wrong." Cameron's comments had come after Trump announced that he supported a ban on Muslims entering the United States.

Papadopoulos's comments were big news in Britain — and the campaign took notice.

J.D. Gordon, a former Pentagon spokesman and Trump national security adviser, said campaign officials were displeased, and Papadopoulos was counseled that he should clear future media appearances with campaign staff and keep a low profile.

"I was surprised to learn what George Papadopoulos was up to during the campaign," he said Tuesday in a text message. "He obviously went to great lengths to go around me and Sen. Sessions."

And yet, Papadopoulos continued to be invited to campaign events. In late June or early July, he attended a dinner at the Capitol Hill Club along with several other national security advisers for the Trump campaign.

Another person who was at the meeting said Sessions also attended; Papadopoulos was seated to Sessions's left.

A spokeswoman for Sessions declined to comment.

Media appearances by Papadopoulos continued.

In September, he spoke extensively to Interfax, telling the Russian news agency that Trump "has been open about his willingness to usher in a new chapter" in U.S.-Russia relations, depending on "Russia acting as a responsible stake holder in the international system." He also questioned the effectiveness of U.S. sanctions on Russia.

By that time, WikiLeaks had released emails hacked from the Democratic National Committee that were widely suspected to have been stolen at the direction of the Russian government. Trump's warm rhetoric toward Putin had become a controversial topic on the campaign trail.

Court documents show that Papadopoulos forwarded a copy of the Interfax article to a Russian woman with whom he had been corresponding during the campaign.

British sources said it was around that time that he approached British government officials to say he was traveling to London and asked to be given a meeting with senior government ministers. Instead, he was offered a session with a mid-level official at the Foreign Office in London.

During the meeting, Papadopoulos made a comment indicating he had contacts at the senior level of the Russian government, British sources said. British officials quickly concluded he was not a major or knowledgeable player in the Trump orbit and did not pursue the issue or continue contact.

A spokesman for the Greek Embassy said he met with that nation's foreign minister in New York. Spokesman Efthymios Aravantinos said the conversation was conducted as part of a routine effort that the embassy makes to reach out to Greek Americans "hoping they have a sentimental attachment to Greece and that we can connect."

It is not clear how much the campaign knew about Papadopoulos's activities. But he continued through these months to have contact with other Trump officials.

In September, Papadopoulos emailed another Trump aide, Boris Epshteyn, and told him he planned to be in New York and hoped to set up meetings around the U.N. General Assembly meeting.

The email was described to The Washington Post in August of this year and is among 20,000 pages of documents that the Trump campaign has turned over to the White House, Congressional committees and defense attorneys.

Papadopoulos wrote that he wanted to connect Epshteyn with a friend, Sergei Millian of the Russian American Chamber of Commerce, the emails said.

Millian would later be identified as a major source for the author of a dossier that included unsubstantiated salacious allegations about Trump's activities in Russia, a claim Millian has denied.

Epshteyn said he never met Millian and declined to comment further. Asked in August to describe his relationship with Papadopoulos, Millian responded by email, "I can meet and talk to any person. . . . It's none of your business."

Millian did not respond to a request for comment Tuesday.

Papadopoulos continued to hold himself out as a Trump adviser, even after the November election.

Two days after Trump's inauguration in January, he met in Washington with a group of Israelis headed by Yossi Dagan, a leader of the West Bank settler movement that prepared a video of the session to be shown at home.

"We had an excellent meeting with Yossi and we hope that the people of Judea and Samaria" — the name used by the Israeli right for the West Bank — "will have a great 2017," Papadopoulos said, according to the video. "We are looking forward to ushering in a new relationship with all of Israel."

According to an account in the Jerusalem Post, the settler leaders had been invited to attend the inauguration and meet with "senators, congressmen and members of the President's team." Dagan, reached by telephone Tuesday in Israel, declined to comment on the visit or who had arranged the meeting with Papadopoulos.

While the president now seems to have left Papadopoulos behind, Papadopoulos has continued to highlight the tie. On LinkedIn, he indicates he was a Trump adviser through January 2017 and includes the experience as the first line of his description about himself.